Metal casting



Aug. 25, 1942.

C. B. FRANCIS ET AL METAL CASTING Filed April 9, 1941 3 Sheets-Sheet l12209211072? (#49455 5. fa /v05,

E0) H NOOEEEE and g- 1942- c.. FRANCIS Ei- AL METAL QASTING Filed April9, 1941 3 Sheets-Sheet 2 v ,M 5 mm m ONEK WZ M i 5w N na If a 4V4 m QPatented Aug. 25, 1942 METAL casrmc Charles B. Francis, PittsburglnandRoy H. Noderer and Ralph B. Porter, Johnstown, Pa.

Application April 9, 1941, Serial No. 387,742

17 Claims.

This invention relates to an improved method and apparatus for thecasting of metal articles f 1arge cross section, and particularly to thecasting of such articles made of either iron or steel, which are thematerials most widely used for such purposes and are also the mostdiflicult to cast properly. Therefore, while the process of ourinvention may be applied in the casting of any metal used in theproduction of articles of large size, we confine the description of thisdisclosure to casting of iron and steel, and to further simplify thedescription of the practice and the explanation of the principles of ourinvention, we restrict thefollowing specification to one example of itsapplication; namely, a large steel roll such as is used in mills for therolling of steel. Any roll of this type has a varying cross section, andsuch rolls frequently. require 20,000

to 100,000 pounds of molten metal, both of whichfactors make the castingoperations difilcult and contribute to the many defects found in suchcastings. Frequently these defects are a cause for the rejection of thecasting and are revealed only after much work has been done upon it.

Besides the defects attributable to improper melting and moldingpractices, large castings of the type in question are subject tootherscon-- sidered unavoidable byrthe practices of the prior art. Theseunavoidable defects result from segregation and changes in volume duringsolidification of the metal and are known as center zone porosity, pipe,cokey texture, dendritie and columnar structures, shrinkage cavities,shrinkage draws and internal-hot tears. -All weaken the casting, andmany are accepted as sufiicient reason for rejection of the casting bythe purchaser.

A principal object of our invention is to eliminate thesedefects-entirely,- while secondary objects are to improve the finishedcasting "and to cheapen the process of manufacture as comtices of theprior art, by decreasing the amount of molten metal required to make agiven cast-' Figure 2 is similar to Figure 1 but shows apparatusembodying the present invention;

Figure 3 is a detail of the apparatus;

Figures 4 and 5 are modifications of Figure 2;

Figure 6 shows the progress of the solidification of the molten casting;

Figure 7 is a vertical sectional view of a sinkhead and associatedapparatus used in carrying out certain, phases of the invention;

Figure 8 is a cross section taken from the line V11IVIII in Figure 7;and

Figure 9 is a modification of Figures 2, 4 and 5.

In these drawings are found the numeral I representing the mold, 2 thecasting and 3 the gate through which the molten metal was introducedinto the mold. By this practice the upper neck 4 of the roll must becast much larger than required by the finished casting, so-that themetal in it will be the last to solidify and will fiow down ward fromthe sinkhad 5 until the metal in the roll proper has-solidified. In sucha mold, solidification of the molten metal progresses very slowly indirections at right angles to the inner surfaces of the mold, and theprogress of solidification may be represented by isothermal lines 6,Following these isothermal lines to the center line ofthe casting, it isobserved that large cavities appear in the sinkhead 5, which representsmetal that has fioweddownward to compensate for the iiquid-to-solidcontraction of the metal below. Usually, the capacity of this sinkheadis approximately $4, of the volume of the mold below it, because themetal freezes from the top of the sinkhead as well as from the sides.

These statements refer w the practices of the prior art. In the completeapplication of our process we employ a mold with a sinkhead hav- '40pared with the cost of manufacture by the pracing a smaller diameterthan the sinkheads of the molds that are used in the practices of theprior art, the sinkheads of our molds having a facing of refractorybrick as illustratedin the drawings, Figures 2, 4, 5 and 6; andwepreheat the interior of this sinkhead to a high temperature Just mentsto refine the structure and the amount 4 of machining ne cessary to bedone after the casting has beenv formed. The following examples sufliceto show how and to what exterrt'; we have succeeded in theaccomplishment of these objects Referring to the drawings, Figurelrepresents a vertical sectional drawingof a large grooved roll as itstands in the mold after casting and solidifying slowly in accordancewith the'practices of the prior art;

prior tb casting, by a method and apparatus described, in a copendingapplication bearing Serial No. 385,172 and filed March 25, 1941.

Below this pipe cavity other cavities of small size are formed about theperiphery of thecasting, starting 1% to 2 inches under the outer sur-'face and extending downward. These small cavities are formed as a resultof selective freezing and segregation, giving rise to pockets of lowmelting constituents that flow downward as the metal below solidifies,and are liable to be exposed in machining this portion of the casting tosize, and are sure to be encountered if the rim'of metal removedbymachining is more v than/ 2 inches thick. 7

To prevent the formation vof these defects is an immediate object of ourinvention, an object we accomplish by controlling both the direction andthe rate or solidification, causing the metal to commence solidifying atthevbottom of the casting and to continuerapidly upward.

Figure 2 represents the design of mold in vertical cross section weemploy to produce the same roll-as that shown'in Figure 1, in which thepart designated bythenumeral is the gate to the mold and the partdesignatedby the numeral 8 is the casting itself. It will be noted,especially, that we have greatly reduced the diameter of the neck 9, andthe size of the sinkhead 10, as compared with the corresponding parts 4and of Figure 1 representing a mold for the same casting made by thepractices of the prior art.

By drawing in isothermal lines I3, marking the advance of solidificationas it occurs naturally,

it can'be' shown that the neck 9 would completely be solid long.before'the metal in the large body below has-solidified, a'conditionthat would rethe upper portion of the .body and across the "suit in theformation of a large pipe located in Another typeofQ feeding e vice whave-Faust- "especially for adding balls-fof. small size; is t e tub isprovided with steel strapsfi Ia which-sup; v

even more satisfactory gthan" that {of Figure '3, open tube of Figure2.1 The lower er'id-g iithis t port a water soaked woodblock 111 such 'adistance below the end of. the'tube'fthatthe,spacef between the uppersurface of the block and the; tube is slightly greater than e-diameter;the balls to be introduced into. the; swirling metal. By properlysupporting thistube atfan-q angle, as shown in the drawings, ballsfedinat; I the upper end first strike the block of wood then 5 tumblegently into the molten metal at'va'rious points, thus preventing theballs'from' descend ing in clusters as are likely to be formed whenf fthe balls'are introduced by any othe'rj imethod Both of these operationsare-carried out in' a" few seconds of time, so that the balls drop-intothe molten metal while itis .stillswirling. The effect of thusintroducing av suitable num ber of balls of propersize isexplainedfasfollows: j};

If the balls should be' introduced after the swirl ceases, they woulddescend ina continuous- 1 before they are'melted,.and these may notmelt' pidly upward," by adding at proper inte lfl a correct quantity ofspecially treated 'iron or-steel-v balls to theliquid steel after it hasbeen poured into the moldi-i'or-by, inserting a bar of iron or @5- steelbefore 'oriafter. casting to" initiate solid'iflca-; tion' at the bottomof the casting, and subse -li-,j 9 quently adding-steel-in the formof'small bodies; such as balls 'orrcub'es. Instead of balls, we may 4use small bodies of iron or steel in various forms such as cubes, shortcylinde'rs or pieces of plates" of irregular shape. Both the size orweight of each body and its shape are important because they affect therate offall and also the rate of For example, spheroidal bodies heattransfer. will fall faster through the liquid and heat up moreslowly-than flat bodies of the same weight.

In order that we maythus control the rate and direction ofsolidification in tallcastings the same-"composition as: that zj offithecasting," in? of the" catti'ng; .I-When the cballsjarerad o 1 ourinventi n;the?mi itia: he' m 1 rated and thrownjpfl center y so thatthey. descend in e; :spiral';pathfiasjr sented by the {line- II in thedrawing'iof Figure 2 completely because of-insufflcient heat as, a reelsuit of thecombined-heatabsorptionof the balls'l "and themoldt wedesireparticularly thatj all of the ba lls in this first; addition should melt;en- 'tirely, "unless; the] balls *are made of steel having.

whichfi case. it A is"fiinniateri'alf whether the balls melt' orniot,as'theybecome bonded with Thus separatedfrom others inlthe column, eac

yball is at-ffirst drawn downward through the 1 f,

having a height of -10 t) inches or more, we proceed as followsz."

First, we introduce the liquid metal-through thegate 'luntil-its topsurface rises. into the l lower part of the sinkli'ead ll), which ispreferably p t i g,

Next by means 'i afile apparatus such as that shown-in'cross section inFigures 2 and, 3, we initiate the first stage of solidification byintroducinga predetermined; Weight of specially byan alloyhaving a lowmeltingpoint, such as -trea'ted-bodies of steelor iron, preferably inthe form of balls. with the apparatus of. Figure 3. the" container,filled'with the required numberof balls, 'is'lowered until its tip ll,which is capped aluminum; just touches the center of the liquid metalsurface, the heat froni which melts the cap almost instantly; so thatthe bottomtip gives way. permitting the balls to 'descend' into themolten metal. -Generally. the surface of the metalis-covered by foreignmaterial gathered as the swirling metal rose in the mold, and to thecenter with a small bar of iron or apole of charred wood iust before thetip of the container 'part in the-process of our-invention; and are memnto ban force of-grayity.

liquid steelby the force of g'rjavity, -'the liquid steel having'adensity ofabout 7.25--g. per 0.; c. and the'cold solid balls a densityof about 7.78" g, perc.c. I t ,g The ratesor speeds of descent of theballs, as welliias the direction of descent, play; a--vital"' describedas follows;

I repr sents the I cubic centimeters and'g the As soon-as the'ball.entersthe liquid steelfthis' "force is partly counteracted by.

.- the buoyant force ofthe liquid, which is equal to 7.25 -'Vg times,so; that the Ieflective. downward A force in only 0.53 Va. dynes,-or0.53 g.', and

acceleration caused by gravity is reduced. fron about 32feetpersecondltq slightly lessthan 2.18 i t .7.25),

, feet persecond, per second; mak e maximum i space through which thebail could move in'the flrst second'iabout ,1,09 feet. 'In the liquidsteel the acceleration isfiniuch 'less' and the distance the balltravels the 'flrst second is also much prevent this dirt from beingcarried downward by the rushing of balls, it isbrushed aside from lessthan 11.09 feet per second, because the viscosity'of the liquidmetalcreates a force of dissurfaces lying" horizontally and the resistance oftheir fall is proportional to the horizontal cross square of the speedor velocity of the ball, the fall of the latter becomes constant, thatis, the speed of the ball attains a certain constant or terminalvelocity within 2 seconds, the exact terminal velocity depending uponthe temperature and viscosity of the liquid steel andthe size of theball, as well as the speed with which it enters the liquid.

By experiment we have found that a ball V to inch in diameter, startingfrom'rest at the surface of the liquid steel, reaches a terminalvelocity of about 6 inches per second within a period of about 1.2seconds and a space of to 8 inches. The distances are increased slightlyif the balls are propelled by afforce at a low velocity as the ballsenter the surface of the liquid steel, but if they enter at highvelocity, as when dropped through the air for a distanceiof 20 or 30inches,

the opposing force of displacement is-such that they are forced along apath forming a loop at a depth of 10 to inches, which may propel themagainst the mold wall of the neck of the roll where they may adherepermanently. This eventuality is avoided by introducing the balls from atube-like container, as shown in Figures 2 and 3. By this means we areassured that all the balls will pass below the level of the upper rollneck during the first 2 or 3 seconds of their descent throug'h.theliquid, a result that'is important for another reason also. Other meansmay be employed to obtain a like result.

After a ball has traveled at terminal .velocity for about 2 seconds, ora total distance of to inches in a total time of 3 seconds, its descentbecomes constantly retarded so that the velocity of a l-inch ballbecomes almost zero 8 to 12 seconds later, because, as soon as the coldball contacts liquid steel, it solidifies up to 2% times its weight orvolume of the liquid ,upon its surface, thus increasing its size and itstemperature, so that the effective downward force of gravity isdecreased to about 0.23 Vg and the opposing force of displacement isincreased, not only because of I the increased size of the ball, butalso because the metal at the bottom of the mold is losing heat andbecoming more viscous. This shell of newly solidified metal ordinarilybegins to form 'as soon as contact is made with the liquid steel, but,to permit the ball to drop to a greater depth the first second, we delaythe formation of the shell by special treatment of the balls asdescribed later. Thus we assure that the balls drop rapidly. through theneck, then more and more slowly unsectional area.

The time of holding after pouring before adding the balls is also afactor affecting the maximum size of ball. that maybe used. For example,if

the casting after pouring can be permitted to stand 15 to 20 minutes topermit the formation of a solid shell 1 to 2 inches thick before anyballs are added, larger balls may be used for the first additions thanwhen they are added in the swirl.

Concerning the weight, or number of balls of agiven size, to be added toany casting or any part thereof, this quantity may be calculated fromthe following equation:

:c(ut 0.1451) (0.27 st) su+ (0.145 X at) 1w:

specific heat of the sand in the mold; st, the average temperature ,riseof the'sand; su, the

weight of the sand; 0.145, the specific heat of the flask; at, theaverage rise in temperature of the flask; fro, the weight of the flask;dt, the temperature drop of the liquid steel in cooling to the liquidus;0.15, the specific heat of the liquid steel; 65, theheat ofsolidification of the liquid til they come to rest at points near thebottom of ball we have found may reach the bottom of any i mold andcause solidification of so much metal about it that it will'not melt.We, therefore,

have selected 2 inches as a medium or standard size of the bah that maybeused for any casting, and vary the size from to 3 inches according .tothe size c1 casting, the smaller sizes being used in the smallercastings and the smallest size for first additions in all castings. Forshort or low molds, say less than 72 inches tall, balls smaller than 1inch in diameter are desirable for the first addition, and small, flatthin bodies may be more desirable than tballs for shorter castings, assuch bodies heat faster and fall more slowly than balls since they-fallwith their flat 75 steel; andw, the weight of the steel in the lowerpart of the mold it .is desired to solidify.

In practice we have found it desirable to coolthe liquid steel only to.within 5 or 10 of the liquidus point, as this cooling'permits the ballsto melt and also brings about rapid solidification of the liquid steelthrough the heat absorbing capacity of the mold, which may vary greatlyaccording to the construction of the mold. Now, good casting practicerequires that the steel be poured at as low a temperature as possible toavoid fusion of the sand to the casting, the highest permissible beingapproximately 120 F. above its liquidus,-and we allow 40 F]. drop inthis temperature for cooling eflect in pouring, making the temperaturedrop to be effected by the balls F. or about 50 C. As the specific heatof the liquid steel is 0.15 cal. per gram, the heat to be absorbed is 700.15=10.5 ca'ls, per gram. Now the heat absorbed by 1 g. of the ballsmay be calculated from the formula,

in which 1171. is the heat absorbing capacity in calories of 1 g. of theballs; 0.145 the average specific heat of'steel; tl the temperature risein degrees centigrade to bring the temperature of the balls to thesolidus; 65 the heat of fusion of the balls; 10 the temperature indegrees centigrade above the liquidus; and 015 the specific heat ofliquid steel.

For steels containing about 1.5% carbon, the heat absorbing capacity ofthe balls is found to be about 241 cals. per gram, or 23 times the heatto be absorbed from the liquid steel. With this factor established, wefind the maximum weight of balls to be added from the weight of metal inthe portion of the mold to-be cooled, 1 inch being subtracted from theheight and the diameter, that is, V inch from the radii,.-to allow forvfing upon the composition of the steel, the pourgber of lesser-factors.Incidentally, the volume is approximately the same as theliquid-to-solid 1 contraction of the metal in'this part of the mold,.zwhich weg find by multiplying the volume, less 1 1 the volume ofashell'l inch thick, by'the factor 4.4,; Both methods give the maximumnumber; of balls to.be added, and'we'generally use 75% of thisnumbenincreasing the number, if the pouring temperature is high. Othermethods 01'; quickly finding theproper number of balls to a add may alsobe used. For example, we have J found that 1 ball linch in diameter willlower the temperature sufficiently of 20 cubic inches of liquid metal inlarge castings or 40 cubic inches of metal in small castings, theexactnumber depending. upon the heat absorbing capacity of kthe mold'and theflask. l Qneapparatus we have found suitable for introducing the ballsinto plain rolls at thisstage of*tlie process'is-shown filled with callsin' Figure' It may be made of wood or steel, and

consists essentially of a tube H, provided with a suitable handle i5,and a special tip I4, which of the balls added in accordance with thismethod temperatures, the rate of pouring and a numameter in proportionto the size of casting up to a maximum insert diameter of 3inches. For

. illustration, an 18-inch casting will require an is made of a lowmelting alloy in the form of v used, because thefballsi jam? qr, ss theopening of a'hopper or funnel- For this, reason we prefer a straightower it by machine, or with a small v ,v 7 he balls by the simple methoddei-scribedbelow.

In the casting of certain rolls, for example,

'thos'efwith small, necks and deep grooves, we. have found'itadvantageous to insert a bar of irietalv f the. same compositionas'thecasting. either-T efore or immediately after casting and i Ee QM-ZfiMt, F 11; 1 r atop por n e clo in 'iasnira In general, however, weprefer to covering to'initiate the solidification'asthe botthisipurposewe have found-it feasible to use he-g'at'es which are of the same lengthas the castings withfajmuch smaller bar attached by- -tcm, insteadflofadding balls in the swirl- For 'weldingjto one end of the gate. Incarrying out the process, the gate, thoroughly cleaned, is suspended orlowered coincident with the long axis of the roll, an'd supported sothat its upper endjust protrudes from the liquid steel. After 5 to 20minutes, according to the diameter of the insert 4 bar, the lower endof, the insert bar has melted. Then we lower the upper portion until theattached bar istotally immersed, by which opera tion we are assured thatthe-crystallized column formed by and about the insert bar is loweredthrough the sinkhead and neck into the 'lower part ofthe body of theroll, where it acc rates the cooling of the metal by abstractingmeat andforces the hotter metal upward into the neck and sinkhead, which wedesire to keep fluid until-all the metal in the body has solidified,Subsequently, we make additions of balls as when no insert insert of 1inch diameter. Three inches is the maximum diameter of bar which willmelt in the cast molten metal within the 20-minute pemediately followingthe first addition of balls.

Consequently, as soon as the first lot of ballshave been introduced intothe swirling metal, the ladle is moved over the sinkhead, which is thenfilled to,the top with liquid steel. Any dirt on the surface of thesteel is rakedofi, and the metal is covered by an exothermic insulatingmixture of nonmetallic substances such as that sold under the trade nameof Lunkerite to prevent a crust .forming onthe surface. This mixtureconsists of powdered aluminum, alumina, fiuorspar, and calcium carbide,and reacts with both iron oxide and the oxygen of the air to produceheat and form at first a fluid slag which later becomes very viscous ora brittle solid. In casting rolls shorter than 100 inches we may notattempt to add balls until the mold is full, when we may add the firstlot of balls just before the top covering is applied except about theedges of the sinkheads which should be covered as soon as possible toprevent the formation of a thick crust of metal. Y

. Withthis mixture the method we have found most satisfactory forapplication in the addition of the steel balls to both large and smallcast- ;ings is illustrated by Figure 4. By this method :we-proceed asfollows: v

As soon as the sinkhe'ad has been filled with molten steel and the dirtskimmed off and the first lot of balls added, if these have not beenpreviously added in the swirl; we add the exothermic covering mixture toa depth of about inch,'and place upon this covering a charred woodblock, which is in turn immediately covered with finely crushedbituminous coal to prevent the block from burning.

This block is 2 to 3 inches thick, and is l to 2 inches smaller in otherdimensions than the section of the sinkhead. It contains a hole at itscenter slightly larger than the largest ball to be added to the liquidsteel, and as soon as,

or before, the block is placed upon the covering, this hole is filledwith the exothermic covering mixture and covered with a piece of boardgso that the coal poured upon 'the block cannot get into ,the hole orbecome mixed with the exethermic covering mixture. By brushing aside thecoal, removing the piece of board, entry to the molten steel beneath theexothermic covering may be had at any time by pushing a rod through themixture'filling theho'le in the block.

- After a period of 5 to 10 minutes has elapsed,

weproceed with the second step of our process,

which is represented by Figure 4. By this time solidification of themetal at the bottom of the mold has progressed inward and upward, asindicated by the isothermal lines 20, and the casting is in a conditionto receive more balls. Be-

iore these balls are added, a circular metalshield bar is usedinitially.The insert will vary in (11- to use a, shield. To addthe balls, a holeis punched through the insulating cover at the center of the wood block,which is over the center of the sinkhead, and the additional ballsrequired to initiate solidification to the level desired are fed slowlythrough a tube or trough 24, to drop through the center hole in the woodblock. Since these balls descend in a straight line coincident with thecenter line of the casting, they are added slowly, the 1-inch balls atthe latent 1 per second and the 2-inch balls at the rate of 1 every 2seconds. To assure that all, or the greater portion, of these balls willbe melted, a number sufiicient to initiate solidification only in thelower half 'of the body are added at this stage,'and thenumber requiredto obtain this result is calculated as expla n d above for those addedwhile the metal is swirling. Usually the weight of balls added in thissecond step is 2 or 3 times the weight of those added in the first step,but seldom more than /4 of the total to be added.

As soon as these balls have been added, the shield is set aside, thehole in the center of the wood block is filled with the exothermiccovering mixture, the piece of board is placed over the hole and theblock is covered with coal as before.

After another interval of to 20 minutes, the hole in the wood block isopened, and the level to whichsolidification has progressed isdetercovering as described above for the second step of the process. Ifthe metal has sunk to a. depth in the sinkhead, we have found itconvenient to brush the coal covering the wood block aside, which soonpermits it to burn through at the center, and then to introduce theballs with the apparatus of Figure 3, as described for the first step ofthe process. After this final addition of balls, the metal remainingmolten in the sinkhead is again covered by adding more of the exothermicor thermite mixture and another charred block of wood, as previouslydescribed herein.

By proceeding in this manner, we bring about rapid solidification of thecasting from the bottom upward, leaving, after the final addition ofballs, only the metal in the neck to solidify. The

withdrawing it quickly and measuring the length upon which metal hassolidified upon its surface,

The final addition of balls to initiate solidification of the metal inthe upper half of the body is made in one or more lots 1 to 3 hoursafter pouring, the exact time of adding each lot, as well as the numberof lots, being determined y the size of the casting and the diameter ofthe neck, for it is evident the addition or additions must be madebefore solidification in the neck 26 of Figure 5 has progressed towithin about- To find the maximum- 6 inches of the center. time intervalafter casting, we assume that solidification has advanced inward fromthe wall of the neck a distance of 1 inch in a time of 1 minute afterpouring and that thereafter solidification advances at a rate measuredin inches whch varies inversely as the square of the time measured inminutes. At this rate, it requires about 1 hour for a shell 1% inchesthick to solidify about the walls of the mold, but solidification in theneck may be faster and the metal in this part of the mold may become soviscous that any balls added will not pass through it. The exact timewhen the addition of balls should cease can be judged by the speed with.which the gage rod descends and the amount of metal that solidifies uponitduring the 3 seconds of its exposure to the liquid steel. Thus, theinsertion of a gage rod into the liquid steelin the mold becomes a meansby which we control the solidification and also a means of ascertainingwhen the addition of balls should cease.

The number of balls to add at this stage may be found by calculationfrom the volume of metal enclosed by the third isotherm (see 25 ofFigure 5), and are to of the number added in the second step. Tointroduce these bails, one of twoprocedures may be used. If the metal inthe surface of the sinkhead has not sunk per- .ceptibly, the balls maybe introduced through the hole in the Wood block and the insulating thedrawings of Figure '7, showing the shield in progress of thesolidification is illustrated by the isotherms 3| of Figure 6, in which30 represents the grating to the mold; 32 the portion solidified by. thefirst addition of balls; 32 the portion solidified by" the secondaddition of balls; 32 the portion solidified by the third addition; and32 the portion solidified by the fourth addition, leaving only the metal34 in the neck 33 in the liquid state to be fed by the liquid steelinthe preheated sinkhead 35, which metal is protected by the covering oithe thermite mixture and charred wood. The sunken top portion 36 we fillwith the hot charcoal and coke formed up to the final operation, andcover this with a heavy layer of crushed bituminous coal to preventrapid heat loss through the top of the sinkhead.

The construction of the shield used for adding the balls in the secondstep, after the mold has been filled with liquid steel, is indicated byvertical cross section, and of Figure 8. showing a cross section of thebottom part of the shield and of the chute'thr'ough which the balls areThis shield is preferably provided with a top portion ll, provided witha peep hole 40.

The composition and preparation of the balls require explanation. Withrespect to composition, the balls may be made from any grade of steeldesired without markedly aifecting' the results obtained with regard tosolidification and the elimination of columnar and dendritic structuresand other causes of center zone weakness. To accomplish these objects,we prefer the balls to be made of steel having the same composition asthe rest of the casting, because there is no danger that these ballswill produce hard or soft spots in the roll if they fail to meltentirely. However, the balls may be of any composition desired, and itis thus possible to alter the composition of the steel in the interiorportion of a casting to improve its toughness, or strength andductility. Thus, it is possible to produce a kind I castor oil and partscrude turpentine. I

turpentine is. added to the castor oil to thin it; This mixture is addedto the soy bean or linseed tings from the lathes, or other discardedparts of castings, a procedure that simplifies the problem of providingballs having the same composition as the castings.

The preparation of the balls is important. To avoid starting gas formingreactions within the steel of a casting and assure perfect bondingbetween the cast metal and any balls that may fail to be completelymelted, the balls must be free from scale, rust or iron oxide in anyform as well as from any other foreign matter, such'a's dust, sand,clay, or other dirt. To obtain these qualities in the balls and alsoprovide a method whereby the balls maybe prepared at any time convenientand used at any subsequent date, we treat them as follows:

To avoid absorption of hydrogen and supply heat to the solution, wefirst heat the balls to a dull red color, then transfer them to a basketmade of acidproof metal and immerse them in a 6% to 10% solution ofsulphuric acid until all scale and oxide are removed. We then rinse themin a 1% solution of hydrochloric acid to remove the ferrous sulphate,dip them in a 5% oil, and the slushing oil is then added to the mixture.5 E

Figure 9 illustrates a special modification of the process of ourinvention, adapting it to the production of rolls and similar articleshaving an extremely wide body section. In this drawing,

which is a vertical section through the center of the casting as itstands in the mold, 46 represents the gate through which the liquidmetal is introduced into the mold and 41 the-casting itself. In sucha'casting the extremely wide body makes it difiicult to build a moldthat will cause upward solidification of the liquid metal to progressuniformly across the section by the simpler procedure described above.Failure to accomplish this object leaves'a zone of unsoundness in thecasting that occurs as an annular ring a few inches inward from theouter surface of the body. We' overcome this difiiculty and produce asound casting by modifying the construction of the mold and the methodof introducing the bodies of solid metal as follows:

In constructing the mold we build into it one or more steel tubes, 48and 49, at a point or points suitably located between the outercircumference 50 of the body of the roll and of the neck 5|.

Each of these tubes has a straight wall except at the bottom near theoutlet tothe mold, where the wall of the tube is indented at point 52 tohold a neatly 'fitting ball 53, which descends with the The smallparticles of solid of copper wire. The tubes are inserted when the moldis prepared. and filled with the small particles of steel after the moldhas been set up for machine or under a steam hammer.

casting.

With the mold thus prepared and mounted, the procedure in casting is asfollows:

First, we will fill the tubes 48 and 49 with the cold steel to be addedto the liquid steel to initiate the solidificationof the molten steel inthe body of the roll. This steel is in the form of small bodies, whichhave been pickled to free them of scale and treated with sodium cyanideand oil to prevent them from rusting, as described for the treatment ofthe cold steel in the form of balls. However, the cold steel weintroduce into the liquid steel, in the present instance, must be in theform of bodies smaller than 1 inch, and may consist of coarse chipsobtained in the rough machining of the castings or of pieces broken inany manner to pass a /2 inch round hole screen. As the steels used forcastings are generally high in carbon and alloys that give a very hardmetal by quenching, we may obtain them by forging the gate runners intoflats less than inch thick, heating the flattened plates to about 1500F., hardening them by cooling rapidly or slowly as required andquenching them in water and breaking them in a crushing ing the tubes 48and 49 with these small bodies steel ball, 53 and 53, that neatly fitsthe inside of each of the tubes 48 and 49, which may vary from 2 inchesto 3 /2 inches in diameter, according to the quantity of steel we desireto add at this point. The total weight of steel to be added isdetermined by the size of the roll body, and the extent to which it isdesired to initiate the solidification, and iscalculated as alreadydescribed for the addition of the balls. With the tubes thus filled withthe pieces of cold steel to be added, the introduction of liquid metalthrough the gate may be started at any time convenient.

The molten metal is introduced through the gate 46 in the usualmanner'until the liquid rises through the neck to a level 51, 6 to 10inches above the top edge of the neck. During this operation the tubes48, 49 are automatically emptied of the charges of small particles ofsteel they contain, as follows:

When the top surface of the liquid metal in the mold rises to the level58, it contacts the bottom of the net 55 and immediately melts thealuminum wire, which ruptures and permits the load of small bodies ofsteelit supports to flow into the liquid steel. Since this metal isswirling at a fast rate, the particles of steel are scat- Then as theliquid continues to rise to level 59, y

it contacts the aluminum net of the second tube, which melts and permitsthe contents 54 of the. tube 49 to descend into the liquid steel 2 or 3inches below the top surface of this portion smaller particles of steel54,. and performs the 'of the mold. The large ball 53 descends with thecontents of the tube and is stopped by the indentation 52, as in thecase of tube 48.

As the metal fills the mold and starts to rise in tubes 48 and 49, itcontacts these large balls and is immediately chilled, or solidified, sothat further upward fiow through these openings is S oppedv at thesepoints.

The metal thus introduced through these tubes is kept near thecircumference by the centrifugal force of the swirl, and by properlyproportioning the cold metal added in this manner to thesize of thebocLv, we cause such a chilling effect that this metal is quicklysolidified against the mold wall by the heat it abstracts, and adJa-iThus,

idly progressing inward towards the isothermal lines I. To make surethat solidification has progressed inward to the loci'of pointsindicated by this line, we cover the surface of the metal in thesinkhead with the exothermic covering mixture previously described andstop pouring through the gate It. After 5 to 10 minutes, we

then introduce a quantityof cold steel in the form of bodies, suchasb'alls, through themface 51, sufllcient to cause solidification toprogress upward to the isothermal line 62, then fill the sinkhead withmolten metal introduced through its top. The top surface of the metal isthen covered as described above for the treatment of rolls with bodiesof smaller diameter in proportion to the neck, and the solidification issequently adding at intervals portions of the treated solid bodies tocause solidification of the liquid metal to advance upward at a rate sothat the body of the roll is practically solid before the metal in theupper neck of smaller diameter has completely solidified.

3. The process of casting rolls of iron and steel, and of causing theliquid metal of which they are made to solidify upwards at a rate fasterthan the solidification in directions normal to the inner surfaces ofthe mold, by the addition at intervals of portions of solid metal in theformof small bodies, which process involves the steps of freeing thesurfaces of the solid bodies from oxide and coating them to prevent themfrom rusting, forming a mold of the desired shape and dimensions with asuitable sinkhead,

- admitting the molten metal through a gate at the bottom of the mold,adding portions of. the solid metal to the liquid metal as itrises inthe mold, filling the sinkhead with the molten metal, covering thesurface of the top of ,the liquid metal with an insulating mixture ofcompounds that made to progress upward in'steps indicated by theisothermal lines 3 and 64, by the addition atintervals of cold steel inthe form of balls, as described previously for the control of thesolid:- ification of the steel in rolls having bodies of :smallerdiameters.

react exothermally with iron oxides and oxygen, placing upon theexothermic mixture a dry charred wooden block with a hole in the center,and subsequently adding at intervals portions of the treated solidbodies to cause solidification of the liquid metal to advance upwar at arate so that the body of the roll is practic lly-solid before the metalin the upper neck of'smaller diameter has completely solidified, saidsolid metal Having thus made a complete disclosure of our invention byexposition and example, we desire to have it understood that variousmodifications may be-made in itsapplication to different metals andcastings of iron or steel without exceed-' ing the scope of ourinvention as defined following claims.

We claim: a

1. The process of producing castings of iron and steel which involvesthe steps of preparing a by 'the I being of a different chemicalcomposition from .that of the liquid metal that is cast.

mold of the desired form and dimensions, introducing the molten metal inthis mold through a gate at the bottom until the mold is filled with theliquid metal, covering the surface of the liquid metal with a mixture ofcompounds that react exothermally with iron oxide and oxygen,

and thereafter adding at intervals portions of I metal, in the form ofsmall scale-free bodies and of a composition similar to that of thecasting,

to cause solidification of the liquid metal of the casting to progressupward at a faster rate than solidification advances'in directionsnormal to the inner surfaces of the mold.

2."!he process of casting rolls of iron and,

steel, and of causing the liquid metal of which they are made tosoiidifyupwards at a rate faster than the solidification in directionsnormal to the inner surfaces of themold, by the addition at intervals ofportions of solid metal in the form of small bodies, which processinvolves the steps of freeing the surfaces of the solid bodies of oxideand coating them to prevent them from rusting, forming a mold of thedesired shape and dimensions with a suitable sinkhead, admitting themolten metal through a gate at the bottom of the mold, adding portionsof the solid metal to the liquid metal as it rises in the mold, fillingthe fsinkhead with the molten metal, covering the surface of the top ofthe liquid metal with an inthat of the liquid metal that is ing a solidbar of metal approximately the same composition as the liquid metal andby the addition at intervals of portions of solid metal in the form ofsmall bodies,- which process involves the'steps of freeing the surfacesof the solid bodies from oxide and coating them to prevent them fromrusting, forming a mold of the desired shape and dimensions with asuitable sinkhead, mounting therein a bar of steel having the samecomposition as the liquid steel and being coincident with the long axisof the casting, admitting the molten metal through a gate at the bottomof the. mold, adding portions of the solid metal to the liquid metal asit rises in the mold; filling the sinkhead with the molten metal,covering the surface of the top of the liquid metal with an insulatingmixture of compounds that react exothermally with iron oxides andoxygen, placing upon the exothermic; mixture a dry charred wooden blockwith a hole in the center, and subsequently adding at intervals portionsof the treated solid bodies to cause solidification of the liquid metalto advance upward at'a rate so that the body of-the roll is practicallysolid before the metal in the upper neck of smaller.diameter hascompletely solidified, said solid metal being of a difierengchemicalcomposition from cast.

5. The process of casting rolls of iron and steel, and of causing theliquid metal of which they are made to solidify upwards at a rate fastethan the solidification in directions normal the inner surfaces of themold, the insertion of solid metal in the form of a bar and by theaddition at intervals of portions of solid metal in the form 0% smallbodies, which process involves the 8 a '1 V j a,294,i7o- L V I steps of,freeing the surfaces of the solid bodies 1 metalimthe mold freely moltenfree from covering the surface of the top of the liquid metal metal inthe moldl'and proportioning."additions from rusting, forming a mold ofthe desired shape 'maining metal'in the mold hasfloccurred; anddimensions with a suitable,sinkhead,.sus- 'i "9'.' Theprocessfofcastingferrousmetalfor pending a cleaned solid barwithin the moldhibitin'gf formation of internal vdefectsand -u along the central axisof the casting, admitting "soundness-iii the finished -casting". duringsolidi the molten metal through a gate at the bottom ficationfof themetal being-ca whichjcomprises; of the mold, covering the top surface ofthe introducing' molten-metal intoa'stationary-open molten metal with anexothermic mixture, then (top, mold addin'g pieces oflmetal in solidfbr'mf lowering the remainder of the suspended bar 10' into themolten-metal throu'gh'the open top of downward through the sinkhead andthe upper I l the mold so that-{the pieces'are' caused to neck into thebody of the roll, and subsequently I Q into the me'talthrough-thesurface of 'the molten from oxide and'coating them to prevent themsolidf crust until after. solidification ofthe re with an insulatingmixture of compounds that and amounts'bf'the said piece'sil to themolten react exothermally with iron oxides and oxygen, metal foreffecting acontliqlled accelerated .up g placing. upon the exothermicmixture a dry wardcooling and upwa'rd 'sol idificatidn ratev or vcharred wooden block with a hole in the center, moltenmetal"substantially morezrapid-ftha'ri lat-5* and subsequently adding atintervals portions of eral cooling thereof, wherebytth e "molten metalthe treated solid bodies to cause solidification of solidifiesprogressively upwardly from the bottom the liquid metal to advanceupward at a rate so of "the-mold substantially rfast'erxithan from thethat the bod of the roll is practically solid before sides thereof,while causing the solid pieces'being the metal in the upper neck ofsmaller diameter added tomeltjprior to theircontactin'g' the solidi hascompletely solidified, said solid metal being I 5 of a differentchemical composition from thatjof, the liquid metal that iscast. a

6. The process of "producing castings ofiron and steel which consists ofthe steps'of preparing" a mold of, the desired form and dimensions, saidmold having a sinkhead with a refractory facing, Y o v I I heating theinterior of the .sinkhead to a high restricted neck 'and a. bottomrestrictedneckwit temperature, introducing the molten metal into a bodyintermediate the necksgreatly ,large the mold through a gate at thebottom until the than .the said'necks, which'comp'rises' making a moldis filled with the liquid metal, covering the mold having approximatelythe configuration of surface of the liquid metal with amixture, ofthecastingso that when the mold is filled, the compounds that reactexothermally withiron metal will be cast into the aforesaid necks andoxide and oxygen, and thereafter adding at in- :b0dy,'-'fi1,1ing'thesaid mold with moltenzfmetal. tervals portions of solid metal, in theform of, iywhile maintaining the top restricted"neck open, smallscale-free bodies, to cause solidification of ,a'dding into the moltenbody of metal in the i, the liquid metal of the casting to progressupmold through the open top neck, pieces o'fmetal ward atafaster ratethan solidification advances 40 in ol 1111. allowing the Said pie toSink in directions normal to the inner surfaces of the through the bodyof metal in'the-mold, proper-- mold. tioning additions and amounts ofthe said pieces 7. The process "of making steel castings inhibto themolten metal for effecting a controlled iting formation of internaldefects in the casting Jacceler'ated upward cooling and upwardsolidifiduringsolidification 1 of the metal being'cast, '45 cation rateof molten metal substantially more which comprises introducing moltenmetal into a rapid than lateral cooling thereof, whereby the H l andadding solid piecesv of steel proporigmolten metal solidifiesprogressively upwardly tioned as to time of additions and'amount forfrom the bottom of the casting substantially controlling the rate ofcooling of the-metal in faster than from the sides thereof, andmaintainthe mold by accelerating normal progressive upin t t prestricted n k of th stin fr ly ward solidification of the metal in themold until molten and freely open from solid crust until a the upwardsolidification of the metal substan- .after',the entire remainingcasting is solidified. tially exceeds in rate the normal rate of lateral11.".t'he process of producing ferrous metal solidification, whilemaintaining'the top portion castings, such as rolls or the like, whichas cast of the metal in the mold freely fluiduntil after and prior toremoval from the mold having a top solidification of the remainder ofthe metal has restrictedneck and a bottornrestricted neck with "beencompleted. a bodyintermediate to the said necks greatly 8. The processof casting ferrous rolls for inlarger than the said necks, whichcomprises hibiting formation of internal defects and unmaking a moldhaving approximately the configsoundness in the finished casting duringsolidiuration of the casting so that when the mold is fication of themetal being cast, which comprises filled, the metal will be cast intothe aforesaidintroducing molten metal into a mold until the necks andbody, filling the said mold with molten mold is filled, adding pieces ofmetal in solid metal while maintaining the top restricted-neck form intothe molten metal through the top of open, introducing, in requisiteinstallments into, the mold so that the pieces are caused to sink themolten body of metal inthe mold, solid pieces into the metal through thetop surface of the Qof metal, allowing the pieces to sink into themolten metal in the mold, proportioning the adbody of metal in the moldto locations well below ditions and amounts of the said pieces to thethe top restricted neck, proportioning additions molten metal foreffecting a controlled accelerand amounts of the said pieces to themolten ated upward cooling and upward solidification metal for effectinga controlled accelerated up- 'rate of molten metal substantially morerapid ward cooling and upward solidification rate of than lateralcooling thereof, whereby the molten molten metal substantially morerapid than latmetal solidifies progressively upwardly from the oralcooling thereof, whereby the molten metal bottom of the moldsubstantially faster than from solidifiesprogressively upwardly from thebottom the sides thereof, and maintainihgthe top of the of the moldsubstantially faster than from the 4 sides thereof, while causing thesolid pieces of metal being added to melt prior to contact with thesolidified metal of the casting but always below zones of pipe andcavity formation in the casting, and maintaining the metal in the toprestricted neck continuously freely molten and free from crust untilafter solidification of the entire remainder of the casting.

12. The process of producing ferrous metal castings, such as rolls orthe like, which as cast and prior to removal from the mold having anopen top restricted neck and a bottom restricted neck with a bodyintermediate to the said necks greatly larger than the said necks, whichcomprises forming a mold conforming approximately in size and shape tothe size and shape of the resulting rough finished casting, with asinkhead having a capacity not substantially more than the minimumrequired to compensate for total contraction of the casting, whichcomprises filling the mold with molten metal, preventing solidificationof metal at its exposed surface by applying thereto, in order, coveringsconsisting of an exothermic mixture, a charredwood block, and powderedcoking coal, permitting the metal to stand in'the mold until a solidshell of metal is formed around the metal and mold wall, andsubsequently to formation of such shell but while the remaining metal isstill liquid, adding chemically clean solid metal in the form of smallpieces and at controlled intervals and in controlled amounts for causinga controlled solidification of metal upwardly at a rate substantiallygreater than from directions normal to the wall of the, mold.

13. The process of producing ferrous metal castings, such as rolls orthe like, which as cast and prior to removal from the mold having anopen top restricted neck and a bottom restricted neck with a bodyintermediate to the said necks greatly larger than the said necks, whichcomprises forming a mold conforming approximately in size and shape tothe size and shape of the resulting rough finished casting, with asinkhead having a capacity not substantially more than the minimumrequired to compensate for total contraction of the casting onsolidification, the open top restricted neck being between the mold andsinkhead, filling the said mold with molten metal, and thereafter addingportions of clean solid metal, each portion being added at predeterminedintervals of time while controlling the size ofthe pieces and intervalsof time so that the added pieces of metal fuse in the metal assolidification thereof proceeds, and solidification of the metaladvances progressively upwardly at a rate substantially faster thansoldification proceeds horizontally, thereby maintaining the metal inthe top restricted neck of the casting freely liquid until aftersolidification of the remainder of the casting.

14. The process of casting ferrous metal rolls having restricted neckportions and a relatively adding to the molten metal portions of solidmetal I in small pieces at varying intervals of time, controlling theweights and intervals of time of the additions of solid pieces so as toeffect solidification of the metal below the said upper neck be fore acolumn of metal coincident with the central axis of the neck hassolidified, and measuring the progress of thesolidification by quicklyinserting-and withdrawing a, gauge rod just prior to adding solid metalat later intervals for ascertaining the requisite amount of solid metalto bethe molten metal to points beneath zones of formation of internalcavities of the casting, proportioning the additions and amounts of thesaid pieces for efiecting a controlled accelerated up- 10 minutes, thetotal metal thus added being from between about 0.5% and about 2.0% ofthe weight of the casting, the weight of each portion added being lessthan about 0.2% of the weight of the casting, and the size of the piecesadded being varied according to the time of addition and the size of thecasting so that they will fuse with the cast metal preferably beforesolidification there-v the pieces during predetermined time intervalsfor effecting a controlled accelerated upward cooling and upwardsolidification rate of molten metal substantially more rapid thanlateral cooling thereof by abstracting heat by the solid pieces from themolten metal from the bottom thereof upwardly, whereby the molten metalsolidifies progressively upwardly from the bottom of the moldsubstantially faster than from the sides thereof, and maintaining thetop of the metal in the mold freely molten and at least substantiallyfree from solid crust until after solidification of the remaining metalin the mold has occurred.

17. The process of casting ferrous metal for inhibiting formation ofinternaLdefects and unsoundness in the finished casting duringsolidification of the metal being cast, which comprises introducingmolten metal into a mold until the mold is filled, adding small piecesof metal in solid form into the molten metal so that the pieces contactthe bottom portion of the molten metalin the mold, and makingpredetermined additions of pieces the predetermined time intervals -foreflecting a controlled accelerated upward cooling and upwardsolidification tate of 1 nolten metal substantially more rapid thanlateral cooling thereof by abstracting heat by the solid pieces mm themolten metal from the bottom upwardly, whereby the molten metalsolidithe mold 'su thereof.

bstantially iaster than trom the sldea SJ .crs; I ROY HtNQDERERQ

